Purging Malawi's peanuts of deadly aflatoxin

Local efforts to put an end to aflatoxin outbreaks are helping groundnut farmers back to prosperity, reports Charles Mkoka.

For Amos Katosa, a subsistence farmer in Malawi's central region district of Mchinji, the groundnut — popularly known as the peanut— has been his main source of income for the past 40 years.

He describes how the crop helped to pay school fees for his four children and to buy household necessities for his family.

But over the past few decades, peanut sales have been declining at commodity markets.

Little did farmers like Katosa know, but the groundnut, once their best income earner, was facing a major challenge that would jeopardise Malawi's contribution to the international export market.

The challenge was aflatoxin, a highly potent poison contaminating crops and rocking Malawi's groundnut industry, which could no longer meet international standards of quality.

Cost of the problem

Aflatoxins are a waste product from the fungus Aspergillus, which grows on food crops such as maize, groundnuts, sorghum and cassava.

The fungus grows on harvested crops under warm, moist conditions that can occur during transit and storage. Unripe crops are also prone to aflatoxin contamination during drought.

Because of the toxicity of aflatoxins, the European Union — an important trading partner for Malawi — effectively banned the import of groundnuts from the country in the early 1990s because contamination exceeded acceptable levels.

A groundnut plant

Credit: Flickr/Megan Choo

The European Union limits aflatoxin contamination to four parts per billion, a standard that has cost some developing countries hundreds of millions of dollars in export losses.

The problem, according to Rodomiro Oritz, from the International Maize and Wheat Improvement Centre, is that monitoring for toxins and enforcement of standards are rarely effective in the developing world, particularly in Sub-Saharan Africa.

Cost to health

In developing countries such as Malawi, the best-quality foods tend to be exported, whereas poor-quality food — often contaminated with aflatoxins — is kept for local consumption.

Children exposed to aflatoxins can suffer from restricted growth and from immune suppression, making them more susceptible to HIV and malaria. Aflatoxins are also strongly associated with the development of liver cancer.

According to Charles Dzamalala, a pathologist at the University of Malawi, acute aflatoxicosis is widespread in developing countries.

The syndrome can be fatal and is characterized by vomiting, abdominal pain, pulmonary oedema, convulsions and coma, and damage to the liver, kidneys and heart.

"Conditions increasing the likelihood of acute aflatoxicosis in humans include limited availability of food, environmental conditions that favour fungal development in crops and commodities, and lack of regulatory systems for aflatoxin monitoring and control," he said.

In 2004 in Kenya, 300 people became ill after consuming aflatoxins, leading to the deaths of 125 people.

Lasting solutions

In Malawi, the challenge presented by aflatoxins has seen the launch of a nongovernmental organisation, Facseat–Tropical.

A young Malawian farmer
at market

Credit: Flickr/mick y

The organisation promotes food-safety measures, including the prevention of fungal contamination of crops, sorting and removal of contaminated grains, and increasing awareness of state-of-the-art facilities for grain storage.

The organisation plans to assess these measures to determine whether they can be linked to any changes in the pattern of liver-cancer incidence, food poisoning or toxicity in the population.

The National Smallholder Farmers Association of Malawi (NASFAM) is collaborating with the International Crop Research Institute for Semi-Arid Tropics (ICRISAT) and the United States Agency for International Development to help farmers meet the aflatoxin safety requirements for export markets.

This involves promoting good agricultural practices, including early planting to prevent groundnuts from maturing during potential drought conditions at the tail end of the season — which can encourage growth of Aspergillus on ripening crops — and appropriate harvesting and drying techniques to reduce the possibility of Aspergillus infection.

NASFAM is also encouraging the use of hand-operated or mechanised shelling equipment to ease the task of shelling. Much of the aflatoxin contamination in Malawi arises from moistening the unshelled nuts to make them easier to shell. The association also encourages farmers to sell their groundnuts immediately after shelling because storage increases the risk of contamination.

NASFAM has recommended organising a national conference to initiate awareness on issues surrounding aflatoxins and their effects on agriculture, health and trade.

The association has so far trained 803 staffers and farmers as part of its capacity-building process to fight aflatoxin contamination, and is setting up a system to trace contamination back to the source.

Catching the culprit

Detection of trace amounts of aflatoxins has recently become much easier for developing countries, thanks to the development of inexpensive enzyme-linked immunosorbent assay (ELISA) kits (see Farmers use cheap technology to fight fungus).

At about US$1 per sample, ELISA is a testing tool that individual farmers can afford; the exorbitant cost of assay by high-performance liquid chromatography (HPLC), used by pre-shipment inspection agents costs around US$230 per sample.

A Malawian woman roasting
groundnuts

Credit: Flickr/Josh Wood

The ELISA kit uses monoclonal and polyclonal antibodies to detect aflatoxins in crop and feed samples. Even remote rural farms can use a small, mobile kit to monitor grains and nuts and to improve storage techniques.

The kit also enables crops for export to be screened rapidly, reducing the risk of infection of other crops.

ICRISAT has established diagnostic laboratories in India, Malawi and Mozambique, which can assay up to 300 samples daily versus the HPLC methods, which can analyse between 20–40 samples a day. This has resulted in safer products for consumer and higher returns for African farmers.

A safer future

Zuberi Seguni, principal agricultural research officer at the Mikocheni Agricultural Research Station in Tanzania, says the technology represents a real saving for farmers.

It should eventually benefit local populations too, as crop quality and storage methods improve.

These new developments have prompted Amos Katosa and many other farmers to give groundnuts another chance, wise to the potential value of the crop both locally and internationally.

"During this crop season, which commences in October, I am certain to reserve two hectares of my garden for groundnuts; this is the crop that has supported me since time immemorial," he says.